I'm writing an app in Angular 2 and I want to execute several http requests and run a function on the responses.
In Angular 1, I would write something like $q.all([$http.get(...), $http.get(...), ...]).then(doSomethingWithResponses);
But Angular 2 returns RxJS Observables and after a bunch of reading I still can't figure out how to get the responses of several http requests. How can this can be done?
As @Eric Martinez pointed out, there is forkJoin. forkJoin runs all observable sequences in parallel and collect their last elements.
Rx.Observable.forkJoin([a,b]).subscribe(t=> {
var firstResult = t[0];
var secondResult = t[1];
});
I'm not sure you'd want to use forkJoin/zip, especially considering combineLatest is easier to understand and will emit on every sub-stream event, whereas forkJoin basically samples on every sub-stream having emitted.
This might come to bite you later when you want to combine multi-item Observables down the road.
Wouldn't a merge work? You can subscribe and attach a handler to the onComplete callback.
I first build an array of my observables and then use static merge:
let obs_ary: any = [obs1, obs2, obs3];
Observable.merge(...obs_ary);
I'm learning RxJS and I was trying to do the same thing with RxJS v5
It seems like we don't have forkJoin on v5 anymore, so here's how I got it working (works with flatMap or mergeMap, which are aliases):
const callOne = value =>
new window.Promise(resolve =>
setTimeout(() => resolve(value + 10), 3000)
);
const callTwo = value =>
new window.Promise(resolve =>
setTimeout(() => resolve(value + 20), 1000)
);
Rx.Observable
.of(2)
.do(() => console.log('querying...'))
.mergeMap(number =>
Rx.Observable.zip(
Rx.Observable.fromPromise(callOne(number)),
Rx.Observable.fromPromise(callTwo(number))
)
).concatAll()
.subscribe(createSubscriber('promises in parallel'));
